You're stating that they're not guilty until caught in the act.

What percentage of the population do you think scrutinizes every credit card statement line-by-line? Many people would not notice an unauthorized charge on their card. It's merely a matter of scale: some people will notice a single unauthorized charge for $5, while others won't even notice $500. Credit card fraud is rampant, and any company that willingly allows its employees to get away with it should be shut down. My experience shows that my city's taxi companies consider credit card fraud as something that doesn't even register on their radar. Drivers that operate in this manner should be criminally charged. It's not just fraud to the taxi company - it is a criminal act of theft for the customers.

Innocent until proven guilty is a cornerstone of the US judiciary system. So yes, they aren't guilty until caught (proven) because their innocence is assumed otherwise.

Not for employment law in most cases (uk/US derived law) you can be fired collectively i.e. if 1 person in a group is skimming but you cant find which one you can fire every one

Until chip and pin this was thing in some uk restaurants waiter used a black (of the books) cardreader out of sight of the punter to skim your card.

They still can do that. The only difference is that they would then sell the numbers to be used online, instead of running as fraudulent card-present transactions.

At least in Canada, portable card readers are the norm. Specifically to counter fraud, you no longer expect to hand your plastic over to an employee who brings it behind the bar. They come to you with a wireless machine, and you insert your own card. It blows my mind how the U.S. is 10-15 years behind the rest of us; the technology behind "debit cards" in the U.S. compared to that of Canada and Europe is almost laughable. The refusal to perform a one-time upgrade to new tech, while continuing to absorb the costs of rampant fraud is completely senseless.